In UMTS (Universal Mobile Telecommunications System) networks, for the purpose of improving spectral efficiency, peak data rates, etc., by adopting HSDPA (High Speed Downlink Packet Access) and HSUPA (High Speed Uplink Packet Access), it is performed exploiting maximum features of the system based on W-CDMA (Wideband Code Division Multiple Access). For the UMTS network, for the purpose of further increasing spectral efficiency and peak data rates, reducing delay and the like, Long Term Evolution (LTE) has been studied (Non-patent Document 1). In LTE, as distinct from W-CDMA, as a multiple access scheme, the scheme based on OFDMA (Orthogonal Frequency Division Multiple Access) is used in downlink, and the scheme based on SC-FDMA (Single Carrier Frequency Division Multiple Access) is used in uplink.
As shown in FIG. 1, signals transmitted in uplink are mapped to appropriate radio resources, and are transmitted from a mobile terminal apparatus to a radio base station apparatus. In this case, user data (UE (User Equipment) #1, UE #2) is assigned to the uplink shared channel (PUSCH: Physical Uplink Shared Channel), and control information is time-multiplexed with the PUSCH when the control information is transmitted concurrently with the user data, while being assigned to the uplink control channel (PUCCH: Physical Uplink Control Channel) when only the control information is transmitted. The control information transmitted in uplink includes downlink quality information (CQI: Channel Quality Indicator), retransmission response (ACK/NACK) to the downlink shared channel, etc.
In the PUCCH, typically, different subframe structures are adopted between the case of transmitting the CQI and the case of transmitting ACK/NACK (FIGS. 2A and 2B). In the subframe structure of the PUCCH, one slot (1/2 subframe) contains 7 SC-FDMA symbols. Further, one SC-FDMA symbol contains 12 information symbols (subcarriers). More specifically, as shown in FIG. 2A, in the subframe structure (CQI format) of the CQI, a reference signal (RS) is multiplexed into a second symbol (#2) and sixth symbol (#6), and the control information (CQI) is multiplexed into the other symbols (first symbol, third to fifth symbols, seventh symbol) in a slot. Meanwhile, as shown in FIG. 2B, in the subframe structure (ACK/NACK format) of ACK/NACK, a reference signal (RS) is multiplexed into third symbol (#3) to fifth sixth symbol (#5), and the control information (ACK/NACK) is multiplexed into the other symbols (first symbol (#1), second symbol (#2), sixth symbol (#6), seventh symbol (#7)) in a slot. In one subframe, the slot is repeated twice. Further, as shown in FIG. 1, the PUCCH is multiplexed into radio resources at opposite ends of the system band, and frequency hopping (Inter-slot FH) is applied between two slots having different frequency bands in one subframe. In the subframe structure of the PUSCH, one slot contains 7 SC-FDMA symbols.